The major active cannabinoid constituent of marijuana, delta9-THC, has been shown to act as a non-toxic anti-tumor agent for a broad range of cancers. Furthermore, it has been demonstrated that treatments combining combinations of cannabinoid constituents from the plant can impart greater activity than any one compound alone. This proposal will focus on the potential treatment of human gliomas using cannabinoids as selective anti-tumor agents. The first aim is to study the anti-proliferative and apoptotic effects of delta9-THC alone and in combination with other major cannabinoid constituents. This will be accomplished using a human glioma cell line that is sensitive to the anti-tumor activity of delta9-THC. The activities of the plant constituents will also be compared to synthetic cannabinoid ligands. CBi and CBi receptors are the primary initial interaction site for the cannabinoid constituent delta9-THC. Activation of the receptor proteins leads to reduced cell proliferation and increased apoptosis in glioma cell lines. When given in combination with delta9-THC, other natural cannabinoid compounds, inactive or less active at the known receptors (CBi and CB2), can produce effects that increase the overall pharmacology compared to the use of a single constituent alone. This potential additive or synergistic effect will be tested against human gliomas. Little is known about the intracellular signaling pathways leading to these effects in human gliomas. The second Aim is to identify the molecular pathways involved in the anti-tumor activity of cannabinoids in a human glioma cell line. This will be accomplished by a detailed study of the pathways that have been implicated in the anti-proliferative and apoptotic effects of the compounds. Using antibody array technology, the search for affected signaling components within the previously identified pathways will be expanded upon and the discovery of novel pathways will also be possible. The final Aim will evaluate the effects of the most active single or combination of cannabinoid constituents on tumor proliferation in brain. In conclusion; combinations of cannabinoid constituents may be more effective anti-tumor agents towards human gliomas than delta9-THC alone. This proposal will test this hypothesis and elucidate the molecular mechanisms responsible for these effects.